In order to provide enhanced control of a dryer appliance, it can be desirable to know the moisture content of articles, such as clothes being dried the dryer. For example, the dryer can be operated until it is sensed that the moisture content of the clothing has fallen below a desired amount. The heater or other appropriate components of the dryer appliance can then be deactivated or otherwise controlled accordingly.
Certain existing dryer appliances use two metal rods in parallel or a combination of rods and the drum surface as a sensor to detect available moisture in the clothing. Other sensors for detecting temperature and relative humidity can be added as well to sense internal air properties. These sensors typically receive excitation power from the dryer control board via a physical connection such as electrical wires. Therefore, the sensors are placed on non-rotating components of the dryer, such as the door or a fixed back wall. However, for many of such sensors, physical contact between the sensor and the clothes being dried is required for accurate sensor readings. Therefore, sensors positioned on the non-rotating components of the dryer, such as the door or a fixed back wall can have less frequency of contact with the entire clothing and do not provide consistently accurate readings.
Placement of the sensors on the rotating components of the dryer, such as the drum or associated lifters or baffles, can result in obtaining more accurate readings at a higher frequency. However, placement of the sensors on the rotating components can present additional problems. For example, wireless communication systems may be required for transmitting the data from rotating components to the non-rotating components.
In addition, one or more local power sources, such as batteries, may be required to power the sensors and the rotating components, including the rotating data transfer components. As such components generally must be powered over the lifespan of a dryer appliance, energy efficiency is a key requirement for extending battery life over the entire lifespan.
Accordingly, improved dryer appliances and methods for operating dryer appliances are desired. In particular, energy-efficient wireless moisture data transfer systems and methods of operation would be advantageous.